Source: Compiled from one or more of the following: raw data from U.S.
Government agency sources, correspondence with POW/MIA families,
published sources, interviews. Updated by the P.O.W. NETWORK in 2018.

"Radio Research" was actually a secret cover designation for certain units
operating under the direction of the U.S. Army Security Agency Group,
Vietnam. All missions of this agency were highly classified. The 224th
Aviation Battalion was referred to as an aviation battalion in Vietnam for
security reasons only. The JU21A aircrew's actual unit designation was 138th
ASA Company, 224th ASA Battalion (Aviation), U.S. Army Security Agency
Group, Vietnam.

Two hours into the mission, at 0840 hours, radio and radar communication was
lost. When the aircraft failed to return from the mission at the appointed
time, search efforts were initiated and continued for 2 days over a 300 mile
area, but proved negative. A reliable source indicated that an aerial
detonation in the vicinity of the DMZ occurred on March 4, 1971 at the same
flight altitude and pattern flown by Vanguard 216. Hostile threat in the
area precluded any visits to the suspected area of the crash. No trace was
ever found of the aircraft or the crew.

While the missing crew members were initially listed as Missing In Action, a
change in status to Killed In Action, Body Not Recovered (KIA/BNR) occurred
within 90 days of the incident. Regarding the status change, the families
were told that all information pertinent to the incident was classified and
would remain classified for ten years.

Since that date, the families have been told that the aircraft was involved
in electronic surveillance, and their mission was top secret. The aircraft
was hit by enemy artillery and was downed over North Vietnam. A "classified
source" stated that the crew was killed. The rest is classified.

Efforts through numerous inquiries, including a Congressional inquiry in
1982, to reveal what information was contained in the "classified source"
have been fruitless. Through the Congressional inquiry, it was learned that
information regarding the loss of Vanguard 216 would be classified until the
year 2010 A.D.

Since American involvement in Southeast Asia ended in 1975, nearly 10,000
reports relating to Americans missing in Vietnam have been received by the
U.S. Government. Most non-government authorities believe there are hundreds
of Americans still alive in the communist prisons of Southeast Asia. The
U.S. Government remains nebulous in their statements, saying only that the
"possibility" exists, but cannot be confirmed.

The crew of Vanguard 216 has been missing for nearly 40 years. The families
of the men aboard hold little hope that they are still alive. But they would
like to know - and deserve to know - what happened on that day. If, as the
U.S. Government seems to believe, all the men are now dead, why the cover of
secrecy regarding their fates? It's time we got answers, and it's time those
who remain alive are brought home.

The last ASA aircraft lost to hostile fire was a U.S. Army JU-21A LEFT JAB
assigned to the 138th Radio Research Company based at Phu Bai, near the DMZ.
On 4 March 1971 it took off on an intelligence-gathering mission. The
aircraft headed northwest towards the DMZ between North and South Vietnam.
Reportedly, the aircraft's mission was to collect intelligence regarding
surface-to-air missile sites, either in the DMZ or just north of it. Shortly
after departure, the JU-21A, tail #67-18062, was shot down.

The crew was declared missing in action. A search effort to locate the
aircraft along its known flight path produced no findings. Those lost were:

CPT Michael W. Marker from Wichita Falls, Texas KIA/BNR WO1

Harold L. Algaard from Fosston, Minnesota KIA/BNR

SP6 John T. Strawn from Salem, Oregon KIA/BNR

SP5 Richard J. Hentz from Oshkosh, Wisconsin KIA/BNR

SP5 Rodney D. Osborne from Kent, Washington KIA/BNR

Retired CW2 Joseph Hayes recalls that day: "I was scheduled to fly on that
aircraft. I had previous morse and DF experience. That morning, I was just
climbing in, when someone came running up to the plane and told me that I
had been bumped. SP6 John T. Strawn jumped on in my place. My duty
assignment as briefing team chief just took priority over this mission. The
CG ASA Pacific, General Wolf, was coming in and a briefing was required. I
was put on the next C-130 out of Phu Bai for Tan Son Nhut. SP6 Strawn and
the rest of the crew took off shortly thereafter and they never landed."

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

A second Congressional inquiry was made on behalf of the
families by
Congressman Bill Young of Florida in May 2010, but additional information
regarding Vanguard 216 was still classified. The “classified source”
that has provided
such limited information over the years has to be NSA. The families of the
Vanguard 216
crewmen have little hope that their loved ones are alive, but they deserve to
know what happened
that day. There is no logical reason why NSA should continue to keep the details
of the incident a
secret. NSA says officially that Vanguard 216 was collecting intelligence
regarding surface-to-air
missile (SAM) sites, either in the DMZ or just north of it, and was “lost to
hostile fire.” Apparently
Vanguard 216 was successful in finding what it was looking for. The aircraft was
almost certainly
brought down by an SA-2 surface-to-air missile. It was the last Army Security
Agency aircraft lost
to hostile fire in Vietnam.

Based on Chapter 29 of Unlikely Warriors: The Army Security Agency's Secret
War in Vietnam 1961-1973